U.S. patent number 7,440,485 [Application Number 10/096,153] was granted by the patent office on 2008-10-21 for apparatus and method for communicating packet data control channel in a mobile communication system.
This patent grant is currently assigned to Samsung Electronics Co., Ltd. Invention is credited to Chang-Hun Bae, Young-Kwon Cho, Ho-Kyu Choi, Woo-Sang Hong, Jae-Sung Jang, Youn-Sun Kim, Hwan-Joon Kwon.
United States Patent |
7,440,485 |
Kwon , et al. |
October 21, 2008 |
Apparatus and method for communicating packet data control channel
in a mobile communication system
Abstract
A base station transmission apparatus for transmitting MAC
(Medium Access Control) ID (Identification) information indicating
a terminal to receive transmission packet data and length
information of the transmission packet data in a mobile
communication system for high-speed packet transmission, having an
encoder for encoding a bit stream indicating the MAC ID information
and generating coded symbols; a Walsh cover section for
Walsh-covering the coded symbols from the encoder with a Walsh code
based on the length information; and a Walsh spreader for spreading
the Walsh-covered symbols from the Walsh cover section with a
predetermined Walsh code.
Inventors: |
Kwon; Hwan-Joon (Seoul,
KR), Choi; Ho-Kyu (Songnam-shi, KR), Cho;
Young-Kwon (Suwon-shi, KR), Hong; Woo-Sang
(Seoul, KR), Bae; Chang-Hun (Seoul, KR),
Kim; Youn-Sun (Seoul, KR), Jang; Jae-Sung
(Kwachon-shi, KR) |
Assignee: |
Samsung Electronics Co., Ltd
(KR)
|
Family
ID: |
27350422 |
Appl.
No.: |
10/096,153 |
Filed: |
March 11, 2002 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20030031230 A1 |
Feb 13, 2003 |
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Foreign Application Priority Data
|
|
|
|
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Mar 10, 2001 [KR] |
|
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2001-0012475 |
Mar 19, 2001 [KR] |
|
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2001-0014161 |
Apr 11, 2001 [KR] |
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2001-0019373 |
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Current U.S.
Class: |
375/140;
375/E1.018 |
Current CPC
Class: |
H04B
1/7093 (20130101); H04J 13/0048 (20130101); H04B
7/2637 (20130101); H04J 13/18 (20130101); H04B
2001/70935 (20130101) |
Current International
Class: |
H04B
1/707 (20060101) |
Field of
Search: |
;375/130,140,146,295 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Burd; Kevin M
Attorney, Agent or Firm: The Farrell Law Firm, PC
Claims
What is claimed is:
1. A base station transmission apparatus for transmitting control
information of packet data in a mobile communication system for
high-speed packet transmission, comprising: an encoder for encoding
information indicating MAC (Medium Access Control) ID
(Identification) information assigned by the base station
transmission apparatus to each mobile station for receiving packet
data and generating coded symbols; a Walsh cover section for
Walsh-covering the coded symbols from the encoder with a
predetermined Walsh code corresponding to length information of a
predetermined subpacket length that indicates the number of slots
constituting a subpacket; and a Walsh spreader for spreading the
Walsh-covered symbols from the Walsh cover section with the
predetermined Walsh code.
2. The base station transmission apparatus as claimed in claim 1,
further comprising a modulator connected between the encoder and
the Walsh cover section, for modulating the coded symbols from the
encoder and outputting the modulated symbols to the Walsh cover
section.
3. The base station transmission apparatus as claimed in claim 1,
further comprising a modulator connected between the Walsh cover
section and the Walsh spreader, for modulating the Walsh-covered
symbols from the Walsh cover section and outputting the modulated
symbols to the Walsh spreader.
4. The base station transmission apparatus as claimed in claim 2,
wherein the encoder is a block encoder.
5. A base station transmission method for transmitting control
information of packet data in a mobile communication system for
high-speed packet transmission, comprising the steps of: encoding
information indicating MAC (Medium Access Control) ID
(Identification) information assigned by the base station
transmission apparatus to each mobile station for receiving packet
data and generating the coded symbols; Walsh-covering the coded
symbols with a predetermined Walsh code corresponding to length
information of a predetermined subpacket length that indicates the
number of slots constituting a subpacket; and spreading the
Walsh-covered symbols with the predetermined Walsh code.
6. The base station transmission method as claimed in claim 5,
wherein the bit stream is encoded by block encoding.
Description
PRIORITY
This application claims priority to an application entitled
"Apparatus and Method for Communicating Preamble Channel in a
Mobile Communication System" filed in the Korean Industrial
Property Office on Mar. 10, 2001 and assigned Ser. No. 2001-12475,
an application entitled "Apparatus and Method for Exchanging Packet
Data Channel in a Mobile Communication System for High-Speed Packet
Transmission" filed in the Korean Industrial Property Office on
Mar. 19, 2001 and assigned Ser. No. 2001-14161, and an application
entitled "Apparatus and Method for Exchanging Packet Data Channel
in a Mobile Communication System for High-Speed Packet
Transmission" filed in the Korean Industrial Property Office on
Apr. 11, 2001 and assigned Ser. No. 2001-19373, the contents of all
of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a mobile communication
system for high-speed packet transmission, and in particular, to an
apparatus and method for communicating control information needed
for demodulation of a packet data transmission channel.
2. Description of the Related Art
In general, a mobile communication system for high-speed packet
transmission is divided into two systems, one system supporting
only data transmission and another system supporting voice
transmission as well as data transmission. The mobile communication
system for high-speed packet transmission is designed to use a
high-speed packet data transmission channel for a high-speed data
service. The high-speed packet data transmission channel (e.g., a
packet data channel (PDCH) of 1xEVDO and 1xEVDV) is shared by a
plurality of users on a time division multiplexing (TDM) basis in
order to transmit data at high speed.
In the mobile communication system for high-speed packet
transmission, a transmitter transmits control information, to
control the transmission of data. The data is transmitted through
the high-speed packet data transmission channel on a TDM basis,
over a packet data control channel (PDCCH), also known as a
preamble channel. To provide a data service through the high-speed
packet data transmission channel, a mobile terminal must receive
control information for the data containing information pertaining
to a destination, a data length, a data rate and a modulation mode,
among others, of the data transmitted at a specific point in
time.
The control information for the packet data includes subpacket
length information, MAC (Medium Access Control) ID, data rate,
modulation mode, payload size, subpacket ID (SPID), and ARQ
(Automatic Repeat Request) channel ID. As mentioned above, in the
mobile communication system for high-speed packet transmission, a
transmission unit of the data transmitted through the high-speed
packet data transmission channel is called a "subpacket", and the
"subpacket length information" refers to the time required to
transmit the data over the high-speed packet data transmission
channel on a TDM basis. A system supporting a variable data length
must transmit this information to the mobile terminals. The MAC ID,
an identifier for mobile terminal identification, is assigned to
the mobile terminal desiring to receive a high-speed packet data
service during system access. The "data rate" is a transfer rate of
data having the subpacket length, and the "modulation mode"
indicates a selected one of QPSK (Quadrature Phase Shift Keying),
8PSK (8-ary Phase Shift Keying), 16QAM (16-ary Quadrature Amplitude
Modulation) and 64QAM (64-ary QAM) modulations used to modulate the
transmission data. The "payload size" refers to the number of
information bits constituting one subpacket, and the subpacket ID
(SPID), an identifier of each of the subpackets, is used to support
retransmission. The ARQ channel ID, an identifier for supporting
continuous data transmission to one mobile terminal, is used in
identifying a parallel transmission channel.
As described above, in the mobile communication system for
high-speed packet transmission, the control information transmitted
over the packet data control channel includes 2-bit subpacket
length information, 16-bit MAC ID, 2-bit payload size, 2-bit SPID
and 2-bit ARQ channel ID, and the data rate and the modulation mode
are determined depending on the 2-bit subpacket, the 2-bit payload
size and Walsh function information used for packet data
transmitted over a packet data transmission channel transmitted
through another channel. Thus, upon receiving packet data after
being assigned MAC ID during system access, a mobile terminal (or
user) desiring to be provided with the high-speed packet data
service demodulates the received packet data control channel and
analyzes the MAC ID to determine whether the received packet is
destined thereto. If so, the terminal demodulates the packet data
using information on subpacket length, payload size, SPID and ARQ
channel ID, acquired by demodulating the packet data and
information on a Walsh function used for packet data channel
transmission. Here, information on a data rate and a modulation
mode of the received subpacket is determined based on a combination
of the subpacket length, the payload size and the Walsh function
used for the packet data channel.
For example, the mobile communication system for high-speed packet
transmission transmits the packet data control information using
two packet data control channels: a forward primary packet data
control channel (PPDCCH) and a forward secondary packet data
control channel (SPDCCH). Such packet data control channels are
utilized along with the packet data channel (PDCH) on a code
division multiplexing (CDM) basis. That is, the forward primary
packet data control channel, the forward secondary packet data
control channel and the packet data channel are assigned different
code channels, and the channels are all transmitted on at the same
time.
As descried above, since the packet data channel and the packet
data control channels are simultaneously transmitted upon, it is
very important for a receiver to promptly demodulate data on the
two packet data control channels without error. Accordingly, there
is a demand for a scheme capable of efficiently transmitting
various control information for demodulation of data on the packet
data channel.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide an
apparatus and method for efficiently transmitting various control
information needed for demodulation of a packet data transmission
channel data in a mobile communication system for high-speed packet
transmission.
It is another object of the present invention to provide an
apparatus and method for covering coded symbols for MAC ID (or
mobile terminal identification) information with a Walsh cover
based on subpacket length information before transmission, in a
mobile communication system for high-speed packet transmission.
It is further another object of the present invention to provide an
apparatus and method for spreading coded symbols for subpacket
length information with a Walsh code based on MAC ID information
before transmission, in a mobile communication system for
high-speed packet transmission.
To achieve the above and other objects, the present invention
provides a base station transmission apparatus for transmitting MAC
ID information indicating a mobile terminal to receive transmission
packet data and length information of the transmission packet data
in a mobile communication system for high-speed packet
transmission. The base station transmission apparatus comprises an
encoder for encoding a bit stream indicating the MAC ID information
and generating coded symbols; a Walsh cover section for
Walsh-covering the coded symbols from the encoder with a Walsh code
based on the length information; and a Walsh spreader for spreading
the Walsh-covered symbols from the Walsh cover section with a
predetermined Walsh code.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other objects, features and advantages of the present
invention will become more apparent from the following detailed
description when taken in conjunction with the accompanying
drawings in which:
FIG. 1 illustrates a structure of a channel transmission device for
transmitting MAC ID information and subpacket length information
according to a first embodiment of the present invention;
FIG. 2 illustrates a modified structure of the channel transmission
device of FIG. 1;
FIG. 3 illustrates a structure of a channel transmission device for
transmitting remaining control information excepting the MAC ID
information and the subpacket length according to the first
embodiment of the present invention;
FIG. 4 illustrates a structure of a channel reception device for
receiving the MAC ID information and the subpacket length
information according to the first embodiment of the present
invention;
FIG. 5 illustrates a modified structure of the channel reception
device of FIG. 4;
FIG. 6 illustrates a structure of a channel reception device for
receiving the remaining control information excepting the MAC ID
information and the subpacket length information according of the
first embodiment of the present invention;
FIG. 7 illustrates a primary packet data control channel (PPDCCH),
a secondary packet data control channel (SPDCCH) and a packet data
channel (PDCH) on a time axis according to an embodiment of the
present invention;
FIG. 8 illustrates a procedure for receiving PPDCCH, SPDCCH and
PDCH by the mobile terminal according to an embodiment of the
present invention;
FIG. 9 illustrates a procedure for transmitting PPDCCH, SPDCCH and
PDCH by a base station according to a second embodiment of the
present invention;
FIG. 10 illustrates a procedure for receiving PPDCCH, SPDCCH and
PDCH by a terminal according to the second embodiment of the
present invention;
FIG. 11 illustrates a structure of a channel transmission device
for transmitting MAC ID information and subpacket length
information by a base station according to the second embodiment of
the present invention;
FIG. 12 illustrates a structure of a channel transmission device
for transmitting the remaining control information excepting the
MAC ID information and subpacket length information by a base
station according to the second embodiment of the present
invention;
FIG. 13 illustrates a structure of a channel reception device for
receiving the MAC ID information and the subpacket length
information by a terminal according to the second embodiment of the
present invention;
FIG. 14 illustrates a structure of a channel reception device for
receiving the remaining control information excepting the MAC ID
information and the subpacket length information by a terminal
according to the second embodiment of the present invention;
FIG. 15 illustrates a procedure for receiving PPDCCH, SPDCCH and
PDCH by a terminal according to a third embodiment of the present
invention;
FIG. 16 illustrates a structure of a channel transmission device
for transmitting subpacket length information by a base station
according to the third embodiment of the present invention;
FIG. 17 illustrates a structure of a channel transmission device
for transmitting the remaining control information excepting the
subpacket length information by a base station according to the
third embodiment of the present invention;
FIG. 18 illustrates a structure of a channel reception device for
receiving the subpacket length information by a terminal according
to the third embodiment of the present invention;
FIG. 19 illustrates a structure of a channel reception device for
receiving the remaining control information excepting the subpacket
length information by a terminal according to the third embodiment
of the present invention; and
FIG. 20 is a diagram for explaining an overall operation of a
terminal according to an embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
A preferred embodiment of the present invention will be described
herein below with reference to the accompanying drawings. In the
following description, well-known functions or constructions are
not described in detail since they would obscure the invention in
unnecessary detail.
In the following description, the specifics such as a length and a
number of the Walsh function used for spreading the forward packet
data control channels (or preamble channels), the type of
information and the number of information bits transmitted through
the packet data control channels are provided by way of example for
a better understanding of the present invention. It would be
obvious to those skilled in the art that the invention may be
implemented without the specifics contained in the examples,
through modification thereof.
The term "forward link" as used herein refers to a transmission
link from a base station to a terminal (or mobile terminal or
mobile station), while the term "reverse link" refers to a
transmission link from the terminal to the base station. In
addition, the term "slot" as used herein refers to a minimum
transmission unit of the forward link, and one slot is 1.25 ms
long.
First Embodiment
FIG. 1 illustrates a structure of a channel transmission device for
transmitting user identification (MAC ID) information and subpacket
length information according to a first embodiment of the present
invention. For example, the channel transmission device may serve
as a PPDCCH (Primary Packet Data Control Channel) transmitter.
Referring to FIG. 1, an encoder 101 encodes 6-bit MAC ID
information into 12 coded symbols. For example, a (12,6) block
encoder can be used for the encoder 101. It will be assumed herein
that the binary symbols output from the encoder 101 are mapped to
+1 or -1 before being provided to a QPSK modulator 102. The QPSK
modulator 102 QPSK-modulates the coded symbols from the encoder 101
and outputs a complex signal comprised of an I-channel signal (real
signal) and a Q-channel signal (imaginary signal). A Walsh cover
section 103 covers the complex signal from the QPSK modulator 102
with a Walsh code (or Walsh cover) of length 4 based on the
subpacket length (2 bits). A Walsh spreader 104 spreads the
Walsh-covered signal from the Walsh cover section 103 with a Walsh
code of length 64. Finally, a PN (Pseudo Noise) spreader 105
spreads the Walsh-spread (or channel-spread) signal from the Walsh
spreader 104 with a PN code and transmits the PN-spread signal.
Although FIG. 1 has been described with reference to the case where
the MAC ID information is comprised of 6 bits, the same structure
can also be applied to another case where the number of MAC ID
information bits has a different value. For example, when the MAC
ID information is comprised of 5 bits, the (12,6) block encoder
used for the encoder 101 must be replaced with a (12,5) block
encoder.
The Walsh code of length 4 used by the Walsh cover section 103 for
Walsh covering is determined by subpacket length information. As
mentioned above, the subpacket length indicates the number of slots
constituting a subpacket. The subpacket length is one of 1 slot, 2
slots, 4 slots and 8 slots. Therefore, when 4 Walsh codes of length
4 are used, it is possible to transmit all of the 4 Walsh codes in
the identifiable form. Table 1 below illustrates how subpacket
lengths are mapped with Walsh codes used for the Walsh covering. In
Table 1, the Walsh codes are mapped by converting binary bits 0 and
1 to +1 and -1.
TABLE-US-00001 TABLE 1 Subpacket Length Mapped Walsh Code 1 1111 2
1-11-1 4 11-1-1 8 1-1-11
As illustrated in Table 1, when the subpacket length is 1 slot, the
Walsh cover section 103 uses a Walsh code `1 1 1 1`. When the
subpacket length is 2 slots, the Walsh cover section 103 uses a
Walsh code `1 -1 1 -1` in Walsh covering the modulated symbols from
the QPSK modulator 102. When the subpacket length is 4 slots, the
Walsh cover section 103 uses a Walsh code `1 1 -1 -1`. When the
subpacket length is 8 slots, the Walsh cover section 103 uses a
Walsh code `1 -1 -1 1`. Table 1 shows only one kind of possible
mappings between the subpacket lengths and the Walsh codes. There
are other possible mappings between the subpacket lengths and the
Walsh codes.
FIG. 2 illustrates a modified structure of the channel transmission
device of FIG. 1. In FIG. 2, the Walsh cover section is arranged
following the encoder.
Referring to FIG. 2, an encoder 201 encodes 6-bit MAC ID
information into 12 coded symbols. For example, a (12,6) block
encoder can be used for the encoder 201. It will be assumed herein
that the binary symbols output from the encoder 201 are mapped to
+1 or -1 before being provided to a Walsh cover section 202. The
Walsh cover section 202 covers the coded symbols output from the
encoder 101 with a Walsh code of length 4 based on the subpacket
length (2 bits). The subpacket length and the Walsh code used for
the Walsh covering are selected from Table 1. A QPSK modulator 203
QPSK-modulates the Walsh-covered signal from the Walsh cover
section 202 and outputs a complex signal comprised of an I-channel
signal (real signal) and a Q-channel signal (imaginary signal). A
Walsh spreader 204 spreads the complex signal from the QPSK
modulator 203 with a Walsh code of length 64. Finally, a PN
spreader 205 spreads the Walsh-spread signal from the Walsh
spreader 204 with a PN code and transmits the PN-spread signal.
Although FIG. 2 has been described with reference to the case where
the MAC ID information is comprised of 6 bits, the same structure
can also be applied to another case where the number of MAC ID
information bits has a different value. For example, when the MAC
ID information is comprised of 5 bits, the (12,6) block encoder
used for the 110 encoder 201 must be replaced with a (12,5) block
encoder.
FIG. 3 illustrates a structure of a channel transmission device for
transmitting the remaining control information excepting the MAC ID
information and the subpacket length according to the first
embodiment of the present invention. As illustrated, the "remaining
control information" may include payload size information, ARQ
channel ID information and subpacket ID (SPID). For example, the
channel transmission device may serve as a SPDCCH (Secondary Packet
Data Control Channel) transmitter.
Referring to FIG. 3, an encoder 301 encodes an information bit
stream corresponding to the remaining control information and
outputs coded symbols. For example, a (48,6) block encoder can be
used for the encoder 301. It will be assumed herein that the
payload size information, the ARQ channel ID information and the
subpacket ID information are each comprised of 2 bits, and the
encoder 301 receives a total of 6 information bits and outputs 48
symbols. A sequence repeater 302 repeats the coded symbols from the
encoder 301 a predetermined number of times according to the number
of slots where the coded symbols are transmitted. The number of
repetitions, the number of time slots occupied by the coded
symbols, is determined depending on length information of packet
data (subpacket length information). A QPSK modulator 303
QPSK-modulates the output signal of the sequence repeater 302 and
outputs a complex signal comprised of an I-channel signal and a
Q-channel signal. A Walsh spreader 304 spreads the complex signal
from the QPSK modulator 303 with a Walsh code of length 64.
Finally, a PN spreader 305 spreads the Walsh-spread signal from the
Walsh spreader 304 with a PN code and transmits the PN-spread
signal.
Although FIG. 3 has been described with reference to the case where
the (48,6) block encoder is used for the encoder 301, the (48,6)
block encoder may be replaced with a (12,6) or (24,6) block
encoder. In this case, a length of the Walsh code used by the Walsh
spreader 304 should be adjusted in order to maintain a transmission
period of the SPDCCH, i.e., a transmission period of the coded
symbols generated by the encoder 301. For example, when the (24,6)
block encoder is used, the Walsh spreader 304 uses a Walsh code of
length 128 for spreading. That is, a length of the codeword (coded
symbols) output from the encoder is in inverse proportion to a
length of the Walsh code used for spreading. In addition, even
though the number of information bits transmitted over the SPDCCH
is not 6, it is possible to transmit the control information in the
same manner by changing the block code used by the encoder 301.
FIG. 4 illustrates a structure of a channel reception device for
receiving the MAC ID information and the subpacket length
information according to the first embodiment of the present
invention. The channel reception device of FIG. 4 has a structure
corresponding to the channel transmission device of FIG. 1.
Referring to FIG. 4, a PN despreader 401 despreads a received
signal with a specific PN code. A first Walsh despreader 402
despreads the PN-despread signal from the PN despreader 401 with a
specific Walsh code used for transmission of the PPDCCH. A second
Walsh despreader 403 despreads the PN-despread signal from the PN
despreader 401 with a Walsh code for a pilot channel. An output of
the first Walsh despreader 402 is provided to an energy measurer
404 and a channel compensator 407. Meanwhile, an output of the
second Walsh despreader 403 is provided to a channel estimator 406.
The channel estimator 406 performs channel estimation using the
pilot channel signal from the second Walsh despreader 403, and
complex-conjugates the channel estimated signal into a channel
compensated signal. The channel compensator 407 performs channel
compensation by multiplying the signal from the first Walsh
despreader 402 and the channel compensated signal from the channel
estimator 406.
The energy measurer 404 and a threshold comparator 405 constitute a
device for determining whether the PPDCCH is received or not. The
energy measurer 404 measures energy of the despread symbols from
the first Walsh despreader 402. An operation of the energy measurer
404 is well known in the art, so a detailed description will be
avoided. The threshold comparator 405 compares a measured energy
value from the energy measurer 404 with a predetermined threshold,
and outputs a packet data control detection signal. As the result
of comparison, if the measured energy value is larger than the
threshold, the channel compensator 407 is enabled in response to
the resultant signal from the threshold comparator 405. This means
a case where the PPDCCH is received at high power, thus enabling
demodulation of the PPDCCH. Otherwise, if the measured energy value
is smaller than the threshold, the channel compensator 407 is
disabled in response to the resultant signal from the threshold
comparator 405. This means a case where the PPDCCH is not received
or received with low reliability, thus disabling demodulation of
the PPDCCH. As stated above, the first embodiment of the present
invention first determines reception and reliability of the PPDCCH
by the energy measurer 404 and the threshold comparator 405, and
then demodulates the PPDCCH according to the determined result. In
order to minimize a processing time, it is possible to perform the
two processes in parallel.
An inverse fast Hadamard transformer (IFHT) 408 performs inverse
fast Hadamard transform on the channel compensated signal from the
channel compensator 407 in a unit of 4 symbols. The reason for
performing the inverse fast Hadamard transform by the IFHT 408 is
to search for a Walsh code (or Walsh cover) used by the Walsh cover
103 of FIG. 1. That is, the signal output from the IFHT 408 in a
unit of 4 symbols becomes correlations between the received signal
and the 4 Walsh codes listed in Table 1. An energy measurer 409
measures energy of the correlations from the IFHT 408. Here, the
energy measurement is performed for one slot where the PPDCCH is
transmitted. The energy measurer 409 measures energy of the Walsh
covers for the one slot. A comparator/selector 410 compares the
measured energy values from the energy measurer 409, and selects
subpacket length information corresponding to a Walsh cover having
the greatest energy value. Here, the comparator/selector 410
includes the mapping table of Table 1, and reads from the mapping
table a subpacket length corresponding to the Walsh cover having
the greatest energy value. The comparator/selector 410 provides the
Walsh cover having the greatest energy value to a Walsh decover
section 411.
The Walsh decover section 411 decovers the signal from the channel
compensator 407 with the Walsh cover from the comparator/selector
410. A QPSK demodulator 412 demodulates a complex signal from the
Walsh decover section 411 into a real signal, and outputs
demodulated symbols. A decoder 413 decodes the demodulated symbols
from the QPSK demodulator 412 and outputs a 6-bit information bit
stream corresponding to the MAC ID information. For example, a
(12,6) block decoder is used for the decoder 413. Although FIG. 4
has been described with reference to the case where the MAC ID
information is comprised of 6 bits, the same structure can also be
applied to another case where the number of MAC ID information bits
has a different value. For example, when the MAC ID information is
comprised of 5 bits, the (12,6) block decoder used for the decoder
413 must be replaced with a (12,5) block decoder.
FIG. 5 illustrates a modified structure of the channel reception
device of FIG. 4. In particular, the channel reception device of
FIG. 5 has a structure corresponding to the channel transmission
device of FIG. 2.
Referring to FIG. 5, a PN despreader 501 despreads a received
signal with a specific PN code. A first Walsh despreader 502
despreads the PN-despread signal from the PN despreader 501 with a
specific Walsh code used for transmission of the PPDCCH. A second
Walsh despreader 503 despreads the PN-despread signal from the PN
despreader 501 with a Walsh code for a pilot channel. An output of
the first Walsh despreader 502 is provided to an energy measurer
504 and a channel compensator 507. Meanwhile, an output of the
second Walsh despreader 503 is provided to a channel estimator 506.
The channel estimator 506 performs channel estimation using the
pilot channel signal from the second Walsh despreader 503, and
complex-conjugates the channel estimated signal into a channel
compensated signal. The channel compensator 507 performs channel
compensation by multiplying the signal from the first Walsh
despreader 502 and the channel compensated signal from the channel
estimator 506.
The energy measurer 504 and a threshold comparator 505 constitute a
device for determining whether the PPDCCH is received or not. The
energy measurer 504 measures energy of the despread symbols from
the first Walsh despreader 502. An operation of the energy measurer
504 is well known in the art, so a detailed description will be
avoided. The threshold comparator 505 compares a measured energy
value from the energy measurer 504 with a predetermined threshold,
and outputs a packet data control channel detection signal. As the
result of comparison, if the measured energy value is greater than
the threshold, the channel compensator 507 is enabled in response
to the resultant signal from the threshold comparator 505. This
means a case where the PPDCCH is received at high power, thus
enabling demodulation of the PPDCCH. Otherwise, if the measured
energy value is less than the threshold, the channel compensator
507 is disabled in response to the resultant signal from the
threshold comparator 505. This means a case where the PPDCCH is not
received or received with low reliability, thus disabling
demodulation of the PPDCCH. As stated above, the first embodiment
of the present invention first determines reception and reliability
of the PPDCCH by the energy measurer 504 and the threshold
comparator 505, and then demodulates the PPDCCH according to the
determined result. In order to minimize a processing time, it is
possible to perform the two processes in parallel.
A QPSK demodulator 508 QPSK-demodulates the channel compensated
signal from the channel compensator 507 and outputs demodulated
symbols. An inverse fast Hadamard transformer (IFHT) 509 performs
inverse fast Hadamard transform on the demodulated symbols from the
QPSK demodulator 508 in a unit of 4 symbols. The reason for
performing the inverse fast Hadamard transform by the IFHT 509 is
to search for a Walsh code used by the Walsh cover 202 of FIG. 2.
That is, the signal output from the IFHT 509 in a unit of 4 symbols
becomes correlations between the received signal and the 4 Walsh
codes listed in Table 1. An energy measurer 510 measures energy of
the correlations from the IFHT 509. Here, the energy measurement is
performed for one slot where the PPDCCH is transmitted. The energy
measurer 510 measures energy of the Walsh covers for the one slot.
A comparator/selector 511 compares the measured energy values from
the energy measurer 510, and selects subpacket length information
corresponding to a Walsh cover having the greatest energy value.
Here, the comparator/selector 511 includes the mapping table of
Table 1, and reads from the mapping table a subpacket length
corresponding to the Walsh cover having the greatest energy value.
The comparator/selector 511 provides the Walsh cover (or Walsh
code) having the greatest energy value to a Walsh decover section
512.
The Walsh decover section 512 decovers demodulated symbols from the
QPSK demodulator 508 with the Walsh cover from the
comparator/selector 511. A decoder 513 decodes the symbols from the
Walsh decover 512 and outputs a 6-bit information bit stream
corresponding to the MAC ID information. For example, a (12,6)
block decoder is used for the decoder 513. Although FIG. 5 has been
described with reference to the case where the MAC ID information
is comprised of 6 bits, the same structure can also be applied to
another case where the number of MAC ID information bits has a
different value. For example, when the MAC ID information is
comprised of 5 bits, the (12,6) block decoder used for the decoder
513 must be replaced with a (12,5) block decoder.
FIG. 6 illustrates a structure of a channel reception device for
receiving the remaining control information excepting the MAC ID
information and the subpacket length information according of the
first embodiment of the present invention. The channel reception
device of FIG. 6 has a structure corresponding to the channel
transmission device of FIG. 3.
Referring to FIG. 6, a PN despreader 601 despreads a received
signal with a specific PN code. A first Walsh despreader 602
despreads the PN-despread signal from the PN despreader 601 with a
specific Walsh code used for transmission of the PPDCCH. A second
Walsh despreader 603 despreads the PN-despread signal from the PN
despreader 601 with a Walsh code for a pilot channel. A channel
estimator 604 performs channel estimation using the pilot channel
signal from the second Walsh spreader 603, and complex-conjugates
the channel estimated signal into a channel compensated signal. The
channel compensator 605 performs channel compensation by
multiplying the signal from the first Walsh despreader 602 and the
channel compensated signal from the channel estimator 604. A QPSK
demodulator 606 QPSK-demodulates the channel compensated signal
from the channel compensator 605 and outputs demodulated symbols. A
sequence combiner 607 sequence-combines the decoded symbols from
the QPSK demodulator 606 based on the repetition frequency of the
sequences used in the transmitter. A decoder 608 decodes the
demodulated symbols from the sequence combiner 607, and outputs the
decoded remaining control information. For example, a (48,6) block
decoder is used for the decoder 608. Here, the "remaining control
information" may include the 2-bit payload size information, the
2-bit ARQ channel ID information and the 2-bit subpacket ID
(SPID).
As described above, in the first embodiment of the present
invention, the MAC ID information and the subpacket length
information are transmitted over the PPDCCH, while the other
control information needed for demodulation is transmitted over the
SPDCCH. Here, the subpacket length information is transmitted by
Walsh covering.
FIG. 7 illustrates a primary packet data control channel (PPDCCH),
a secondary packet data control channel (SPDCCH) and a packet data
channel (PDCH) on a time axis according to an embodiment of the
present invention.
As illustrated in FIG. 7, the subpackets transmitted at the same
time are represented by the same reference letters. The SPDCCH and
the PDCH are transmitted for time durations T.sub.A, T.sub.B and
T.sub.c, while the PPDCCH is transmitted for one slot regardless of
a length of the time durations T.sub.A, T.sub.B and T.sub.c. Here,
the time durations of the SPDCCH and the PDCH may occupy 1 slot, 2
slots, 4 slots or 8 slots according to the payload size and data
rate of the packet data transmitted. The time durations where the
SPDCCH is transmitted, are basically set equal to the time
durations of the PDCH. However, the SPDCCH should be first received
in order to demodulate and decode the PDCH. Thus, when the PDCH
occupies two or more slots, the time durations of the SPDCCH may be
set shorter than the time duration of the PDCH. For example, when
the PDCH occupies 8 slots, the SPDCCH may occupy 4 slots. For the
time durations T.sub.A, T.sub.Band T.sub.c, a process for receiving
the PDCH is initiated by detecting PPDCCH of each time duration.
After successfully detecting the PPDCCH, the terminal restores the
MAC ID information and the PDCH subpacket length information
included in the PPDCCH. If the received MAC ID information is
identical to its own MAC ID information, the terminal restores the
remaining control information by demodulating and decoding the
SPDCCH, and then demodulates and decodes the PDCH using the control
information. Since the PPDCCH, the SPDCCH and the PDCH are
simultaneously received, the terminal should store the SPDCCH and
the PDCH in a buffer during restoration of the PPDCCH, and store
the PDCH in the buffer during restoration of the SPDCCH.
FIG. 8 illustrates a procedure for receiving PPDCCH, SPDCCH and
PDCH by the terminal according to an embodiment of the present
invention. Referring to FIG. 8, the terminal detects PPDCCH from a
current slot in step 801. As described in conjunction with FIGS. 4
and 5, the terminal can detect the PPDCCH by despreading a
PN-despread signal with the Walsh code used for spreading of the
PPDCCH and then measuring energy of the despread symbols. That is,
it is necessary to perform energy detection over one-slot duration
in order to detect the PPDCCH. Therefore, in order to secure a time
required for receiving the PPDCCH and a time required for the
energy detection, the terminal buffers the SPDCCH and the PDCH in a
slot to which the PPDCCH belongs while performing the PPDCCH
detection, and then buffers the PPDCCH, the SPDCCH and the PDCH in
the next slot. The buffering is performed in step 802. The reason
for performing the buffering is because upon detection of the
PPDCCH, the terminal should restore the SPDCCH and the PDCH
received along with the PPDCCH, and even upon failure to detect the
PPDCCH, the terminal should perform the energy detection on the
next slot.
After performing the DDPCCH detection, the terminal determines in
step 803 whether a measured energy value of the PPDCCH exceeds a
predetermined threshold, i.e., whether the PPDCCH is successfully
received. If the measured energy value is greater than the
threshold, the terminal determines that the PPDCCH is received.
Otherwise, the terminal determines that the PPDCCH is not received.
If it is determined that the PPDCCH is not received, the terminal
returns to step 802 and performs energy detection on the buffered
PPDCCH of the next slot. However, if it is determined that the
PPDCCH is received, the terminal restores subpacket length
information received over the PPDCCH in step 804. The subpacket
length information, as described in conjunction with reference to
FIGS. 4 and 5, can be searched by determining the Walsh cover
(Walsh code) used, through inverse fast Hadamard transform and then
consulting the mapping table of Table 1.
After restoring the subpacket length information, the terminal
restoring the MAC ID information received over the PPDCCH using a
Walsh cover of length 4 is calculated through the inverse fast
Hadamard transform in step 805. After restoring the MAC ID
information, the terminal compares the restored MAC ID information
with its own MAC ID information in step 806. If the restored MAC ID
information is not identical to its own MAC ID information, the
terminal returns to step 801 and performs again energy detection on
the buffered PPDCCH of the next slot. Otherwise, if the restored
MAC ID information is identical to its own MAC ID information, the
terminal recognizes that the received packet data channel is
destined therefore, and then proceeds to step 807.
In step 807, the terminal analyzes the subpacket length information
to determine whether a length of the subpacket in the packet data
channel is 1 slot or 2 slots. If the length of the subpacket in the
packet data channel exceeds 2 slots, the terminal additionally
buffers the SPDCCH and the PDCH according to the length of the
subpacket in step 808. For example, if the subpacket length is 4
and the SPDCCH and the PDCH occupy the same number of slots, the
terminal additionally buffers the SPDCCH and the PDCH of the two
remaining slots excepting the two slots of the previously buffered
SPDCCH and PDCH. As a result, the terminal buffers the SPDCCH and
the PDCH of a total of 4 slots.
After additionally performing the SPDCCH and the PDCH, the terminal
performs despreading on the buffered SPDCCH and performs sequence
combining on the symbols created through the despreading based on
the repetition number used by the transmitter, in step 809.
Thereafter, in step 810, the terminal restores the remaining
control information excepting the MAC ID information and the
subpacket length information by decoding the symbols created by the
sequence combining. The remaining control information, as stated
above, includes the payload size information, the ARQ channel ID
information and the subpacket ID information. Thereafter, in step
811, the terminal demodulates and decodes the PDCH using the
control information acquired by restoring the PPDCCH and the
SPDCCH, thereby restoring the packet data.
If it is determined in step 807 that the length of the subpacket in
the packet data channel is 1 slot or 2 slots, the above additional
buffering is not performed. Therefore, in step 813, the terminal
performs despreading on the buffered SPDCCH of the 1 slot or 2
slots, and performs sequence combining on the symbols created
through the despreading based on the repetition number used in the
transmitter. Thereafter, in step 814, the terminal restores the
remaining control information excepting the MAC ID information and
the subpacket length information by decoding the symbols created by
the sequence combining. The remaining control information, as
stated above, includes the payload size information, the ARQ
channel ID information and the subpacket ID information.
Thereafter, in step 815, the terminal demodulates and decodes the
PDCH using the control information acquired by restoring the PPDCCH
and the SPDCCH, thereby restoring the packet data.
Second Embodiment
FIG. 9 illustrates a procedure for transmitting PPDCCH, SPDCCH and
PDCH by a base station according to a second embodiment of the
present invention. Referring to FIG. 9, when a terminal desiring to
receive a packet data service attempts an access in step 901, the
base station determines in step 902 whether there exists available
MAC ID information assignable to the terminal by consulting Table
3. If there exists no available MAC ID information, the base
station performs an access fail process. Otherwise, if there exists
available MAC ID information, the base station assigns one of the
available MAC IDs to the terminal and then informs the terminal of
the assigned MAC ID through a signaling message, in step 903. Being
assigned the MAC ID, the terminal acquires information (Walsh
function information, and information on a channel of the complex
channels, to be used for transmission) on the PPDCCH to be
received, using Table 2 or Table 3 previously agreed with the base
station, and thereafter, detects the PPDCCH using the acquired
information.
TABLE-US-00002 TABLE 2 MAC Using Walsh function assigned to
Transmission channel ID state PPDCCH (I or Q channel) 00000 O Walsh
function No 48 of In-Phase channel 00001 O length 512
Quadrature-phase channel 00010 X Walsh function No 49 of In-Phase
channel 00011 O length 512 Quadrature-phase channel 00100 X Walsh
function No 50 of In-Phase channel 00101 X length 512
Quadrature-phase channel 00110 O Walsh function No 51 of In-Phase
channel 00111 X length 512 Quadrature-phase channel . . . . . . . .
. . . .
TABLE-US-00003 TABLE 3 MAC Using Walsh function assigned to
Transmission channel ID state PPDCCH (I or Q channel) 00000 O Walsh
function No 48 of In-Phase channel 00001 O length 512
Quadrature-phase channel 00010 X In-Phase channel 00011 O
Quadrature-phase channel 00100 X Walsh function No 49 of In-Phase
channel 00101 X length 512 Quadrature-phase channel 00110 O
In-Phase channel 00111 X Quadrature-phase channel . . . . . . . . .
. . .
Table 2 and Table 3 illustrate memory tables required by the base
station in the MAC ID to the terminal desiring to receive the data
service and managing ID information. Specifically Table 2 includes
using state information indicating whether the MAC IDs are in use
at a specific point of time, and also includes information on Walsh
functions used for the PPDCCH according to the MAC IDs and
information on a transmission channel of the complex channels, to
be used for transmission. If the terminal to be provided with the
service is determined by a scheduler, a Walsh function to be used
for spreading of the PPDCCH is determined according to the MAC ID
information of the terminal. After determination of the Walsh
function, the base station selects one of the I (In-phase) channel
and the Q (Quadrature-phase) channel, to transmit the PPDCCH
through the selected channel. Namely, the Walsh function and the
transmission channel are assigned to the MAC ID on a one-to-one
basis (one-to-one mapping). Even though the same Walsh function is
used, the base station can identify the MAC ID using the
transmission channel (I or Q channel) information. This means that
the base station can identify as many terminals as twice the number
of the Walsh functions assigned to the PPDCCH. For example, when 16
Walsh functions are assigned to the PPDCCH, the base station can
identify 32 terminals, which means that the base station can assign
a total of 32 MAC IDs.
Meanwhile, Table 3 is used when transmitting twice the MAC ID
through the PPDCCH and the SPDCCH. As illustrated in Table 3, the
same Walsh function and the same transmission channel are mapped to
a plurality of MAC IDs (e.g., 2 MAC IDs) (multiple-to-one mapping).
Therefore, if the base station transmits the PPDCCH using the Walsh
function and transmission channel corresponding to a specific MAC
ID, then not only the terminal but also another terminal will
demodulate the SPDCCH. In this case, the terminals determine
whether the received packet is their own packet or another
terminal's packet, by analyzing the MAC ID included in the
SPDCCH.
Turning back to FIG. 9, after assigning the MAC ID information to
the terminal, the base station acquires information (Walsh function
and transmission channel) needed for transmitting the PPDCCH from
Table 2 or Table 3. Thereafter, in step 904, the base station
transmits the subpacket length information corresponding to a
transmission length of the PDCH through the PPDCCH. At that moment,
the base station transmits the subpacket length information through
the acquired transmission channel (I channel or Q channel), and
performs channel spreading using the determined Walsh function.
Meanwhile, the base station transmits the SPDCCH and the PDCH in
step 905. At that moment, the base station determines a sequence
repetition number of the SPDCCH and the PDCH according to the
subpacket length information by consulting Table 4 below, and
repeats the coded symbols transmitted over the SPDCCH and the PDCH
according to the determined sequence repetition number.
TABLE-US-00004 TABLE 4 Subpacket length Transmission length of
Transmission length of information SPDCCH PDCH 00 1 1 01 2 2 10 4 4
11 4 8
FIG. 10 illustrates a procedure for receiving PPDCCH, SPDCCH and
PDCH by the terminal according to the second embodiment of the
present invention. Specifically, FIG. 10 illustrates an operation
of a reception device of FIGS. 13 and 14, which corresponds to an
operation of a transmission device of FIGS. 11 and 12. First, the
terminal is assigned a MAC ID from the base station and determines
a Walsh function and a transmission channel for demodulating the
PPDCCH using the assigned MAC ID by consulting Table 2.
Referring to FIG. 10, in step 1001, the terminal obtains symbols of
the PPDCCH by multiplying a PN-despread signal received through the
determined transmission channel (I channel or Q channel) by the
determined Walsh function, for despreading. In step 1003, the
terminal measures energy of the obtained symbols and determines
whether the measured energy value exceeds a predetermined
threshold, i.e., whether the PPDCCH is received. It is necessary to
perform energy measurement over a one-slot duration in order to
determine whether the PPDCCH is received. Therefore, in order to
secure a time required for receiving the PPDCCH and a time required
for the energy measurement, the terminal buffers the SPDCCH and the
PDCH in a slot which the PPDCCH is included while performing the
PPDCCH detection, and then buffers all of the PPDCCH, the SPDCCH
and the PDCH in the next slot. The reason for performing the
buffering is because upon detection of the PPDCCH, the terminal
should restore the SPDCCH and the PDCH received along with the
PPDCCH, and even upon failure to detect the PPDCCH, the terminal
should perform the energy detection on the next slot.
If the measured energy value exceeds the threshold, the terminal
proceeds to step 1005. Otherwise, the terminal proceeds to step
1017 where it discards the SPDCCH and the PDCH buffered after being
received along with the PPDCCH, and then performs energy detection
on the buffered PPDCCH of the next slot. Since the base station
uses a specific Walsh function uniquely assigned to a corresponding
terminal during spreading of the PPDCCH, other terminals except for
the corresponding terminal may fail to detect energy in step 1003.
If the measured energy value exceeds the threshold in step 1003,
the terminal recognizes that the currently received packet data is
its own data destined therefore. Thereafter, the terminal
demodulates and decodes the PPDCCH in step 1005, and acquires
subpacket length information received over the PPDCCH in step
1007.
In step 1009, the terminal determines a transmission length (or
sequence repetition number N) of the SPDCCH using the acquired
subpacket length information by consulting Table 4. If the
transmission length exceeds 2 slots, the terminal additionally
buffers the SPDCCH and the PDCH according to the subpacket length.
For example, if the subpacket length is 4 and the SPDCCH and the
PDCH occupy the same number of slots, the terminal additionally
buffers the SPDCCH and the PDCH of the remaining 2 slots except for
the two slots of the previously buffered SPDCCH and PDCH. As a
result, the terminal buffers the SPDCCH and the PDCH of a total of
4 slots. In step 1009, the terminal despreads the buffered SPDCCH
and sequence-combines the symbols created through the despreading
based on the sequence repetition number. Thereafter, the terminal
decodes the symbols created by the sequence combining in step 1011,
and acquires the remaining control information except for the MAC
ID information and the subpacket length information in step 1013.
Here, the "remaining control information" may include the subpacket
ID information, the payload size information and the ARQ channel ID
information. Thereafter, in step 1015, the terminal demodulates the
PDCH using the control information acquired by demodulating the
PPDCCH and the SPDCCH.
FIG. 11 illustrates a structure of a channel transmission device
for transmitting MAC ID information and subpacket length
information by a base station according to the second embodiment of
the present invention. Referring to FIG. 11, an encoder 1101
encodes subpacket length information into coded symbols. For
example, a (3,2) block encoder for block-encoding 2-bit subpacket
length information into 3 output symbols can be used for the
encoder 1101. A controller 1102 controls an I/Q channel switch 1103
and Walsh spreaders 1104 and 1105 using Table 2. The switch 1103,
under the control of the controller 1102, switches the symbols from
the encoder 1101 to an I channel (first output line) or a Q channel
(second output line). When the switch 1103 is connected to the
first output line, the Walsh spreaders 1104 connected to the first
output line multiplies the symbols on the first output line by a
Walsh function of length 512 from the controller 1102, for
spreading, and outputs 1,536 chips per slot. When the switch 1103
is connected to the second output line, the Walsh spreader 1105
connected to the second output line multiplies the symbols on the
second output line by the Walsh function of length 512, for
spreading, and outputs 1,536 chips per slot. As mentioned above,
the PPDCCH transmitter spreads the coded symbols corresponding to
the subpacket length information with a Walsh function based on the
MAC ID information, and transmits the spread coded symbols through
a specific transmission channel (I channel or Q channel).
FIG. 12 illustrates a structure of a channel transmission device
for transmitting the remaining control information excepting the
MAC ID information and subpacket length information by a base
station according to the second embodiment of the present
invention. As illustrated, the "remaining control information" may
include payload size information, ARQ channel ID information and
subpacket ID information. Referring to FIG. 12, an encoder 1201
encodes an information bit stream of the remaining control
information into coded symbols. For example, a (12,6) block encoder
for block-encoding a 6-bit information bit stream into 12 output
symbols can be used for the encoder 1201. The controller 1102
controls a sequence repetition number of a sequence repeater 1202
based on the subpacket length information. The sequence repeater
1202, under the control of the controller 1102, sequence-repeats
the coded symbols from the encoder 1201 a predetermined number of
times. A QPSK modulator 1203 QPSK-modulates the coded symbols from
the sequence repeater 1202 into a complex signal comprised of an
I-channel signal and a Q-channel signal. Walsh spreaders 1204 and
1205 multiply the complex signal from the QPSK modulator 1203 by a
Walsh function of length 256 assigned to the SPDCCH, for spreading.
Thereafter, the Walsh-spread signal is PN-spread and converted into
a radio frequency. The radio frequency is transmitted through an
antenna.
FIG. 13 illustrates a structure of a channel reception device for
receiving the MAC ID information and the subpacket length
information by a terminal according to the second embodiment of the
present invention. The channel reception device of FIG. 13 has a
structure corresponding to the channel transmission device of FIG.
11.
Referring to FIG. 13, a controller 1303 reads a Walsh function
corresponding to a MAC ID assigned by the base station from Table 2
and provides the read Walsh function to Walsh despreaders 1301 and
1302. Further, the controller 1303 controls a switching operation
of a switch 1304 by reading transmission channel information from
Table 2. The despreaders 1301 and 1302 despread 1,536 chips
received for one slot with a Walsh function of length 512
determined by the controller 1303, and outputs 3 coded symbols. The
switch 1304 is switched by the controller 1303, thus to provide
outputs of the despreader 1301 or 1302 to an energy detector 1305
and a decoder 1306. The energy detector 1305 measures energy of the
symbols from the switch 1304, and outputs the measured energy value
to the controller 1303. The controller 1303 determines whether the
measured energy value exceeds a predetermined threshold. If the
measured energy value is greater than the threshold, the controller
1303 enables the decoder 1306. However, if the measured energy
value is less than the threshold, the controller 1303 disables the
decoder 1306. The decoder 1306, under the control of the controller
1303, decodes the symbols from the switch 1304 and outputs the
subpacket length information. The subpacket length information is
provided to the controller 1303. For example, a (3,2) block decoder
for block-decoding 3 input symbols and outputting 2 information
bits can be used for the decoder 1306.
FIG. 14 illustrates a structure of a channel reception device for
receiving the remaining control information excepting the MAC ID
information and the subpacket length information by a terminal
according to the second embodiment of the present invention. The
channel reception device of FIG. 14 has a structure corresponding
to the channel transmission device of FIG. 12. The channel
reception device of FIG. 14 is enabled when the measured energy
value of the PPDCCH detected by the energy detector 1305 of FIG. 13
is greater than the threshold.
Referring to FIG. 14, despreaders 1401 and 1402 multiply received
PN-despread signals by a Walsh function of length 256 used for
Walsh spreading of the SPDCCH, for spreading, and output 6 symbols
per slot. A QPSK demodulator 1403 QPSK-demodulates the 6 symbols
from the despreaders 1401 and 1402, and outputs 12 demodulated
symbols per slot. The controller 1303 receives the subpacket length
information from the PPDCCH reception device of FIG. 13, and
determines a sequence repetition number N indicating the number of
slots over which the SPDCCH is transmitted, i.e., how many times
the sequence has been repeated, by consulting Table 4 based on the
subpacket length information. Further, the controller 1303 controls
a sequence combiner 1404 based on the sequence repetition number N.
The sequence combiner 1404, under the control of the controller
1303, generates 12 coded symbols by combining the demodulated
symbols from the QPSK demodulator 1403. A decoder 1405 decodes the
12 coded symbols from the sequence combiner 1404 and outputs the
remaining control information. For example, a (12,6) block decoder
for block-decoding 12 coded symbols received and generating a 6-bit
information bit stream can be used for the decoder 1405. Here, the
"remaining control information" may include 2-bit payload size
information, 2-bit subpacket ID information and 2-bit ARQ channel
ID information. The control information acquired in this manner is
used in demodulating the PDCH later.
As described above, the second embodiment of the present invention
transmits the MAC ID information and the subpacket length
information over the PPDCCH and the remaining control information
over the SPDCCH. Here, the coded symbols of the PDCCH are
transmitted after being spread with a unique Walsh code based on
the MAC ID information.
Third Embodiment
FIG. 15 illustrates a procedure for receiving PPDCCH, SPDCCH and
PDCH by a terminal according to a third embodiment of the present
invention. That is, FIG. 15 illustrates an operation of the channel
reception devices of FIGS. 18 and 19, which correspond to the
transmission devices of FIGS. 16 and 17. First, the terminal is
assigned a MAC ID from the base station and determines a Walsh
function for demodulating the PPDCCH and a transmission channel by
consulting Table 3, using the assigned MAC ID information.
Referring to FIG. 15, in step 1501, the terminal acquires symbols
of the PPDCCH by multiplying the PN-despread signal received over
the determined transmission channel (I channel or Q channel) by the
determined Walsh function for despreading. In step 1503, the
terminal measures energy of the acquired symbols and determines
whether the measured energy value exceeds a predetermined
threshold, i.e., whether the PPDCCH is received. Here, it is
necessary to perform energy detection over a one-slot duration in
order to detect reception of the PPDCCH. Therefore, in order to
secure a time required for receiving the PPDCCH and a time required
for the energy detection, the terminal buffers the SPDCCH and the
PDCH in a slot to which the PPDCCH belongs while performing the
PPDCCH detection, and then buffers all of the PPDCCH, the SPDCCH
and the PDCH in the next slot. The reason for performing the
buffering is because upon detection of the PPDCCH, the terminal
should restore the SPDCCH and the PDCH received along with the
PPDCCH, and even upon failure to detect the PPDCCH, the terminal
should perform the energy detection on the next slot.
If the measured energy value exceeds the threshold, the terminal
proceeds to step 1505. Otherwise, the terminal proceeds to step
1519 where it discards the SPDCCH data and the PDCH data buffered
after being received along with the PPDCCH, and then performs
energy detection on the buffered PPDCCH of the next slot. Since the
base station uses a specific Walsh function uniquely assigned to a
corresponding user during spreading of the PPDCCH, other terminals
assigned no Walsh function may fail to detect energy in step 1503.
That is, only the terminals using the same Walsh function will
detect the energy in accordance with Table 3. If the measured
energy value exceeds the threshold in step 1503, the terminal
recognizes that the currently received packet data is its own data.
Therefore, the terminal demodulates the PPDCCH in step 1505, and
acquires subpacket length information received over the PPDCCH in
step 1507.
In step 1509, the terminal determines a transmission length (or
sequence repetition number N) of the SPDCCH using the acquired
subpacket length information by consulting Table 3. If the
transmission length exceeds 2 slots, the terminal additionally
buffers the SPDCCH and the PDCH according to the subpacket length.
For example, if the subpacket length is 4 and the SPDCCH and the
PDCH occupy the same number of slots, the terminal additionally
buffers the SPDCCH and the PDCH of the remaining 2 slots except for
the two slots of the previously buffered SPDCCH and PDCH. As a
result, the terminal buffers the SPDCCH and the PDCH of a total of
4 slots. In step 1509, the terminal despreads the buffered SPDCCH
and sequence-combines the symbols created through the despreading
based on the sequence repetition number. Thereafter, the terminal
decodes the symbols created by the sequence combining in step 1511,
and acquires the remaining control information except for the
subpacket length information in step 1513. Here, the "remaining
control information" may include the MAC ID information, the
subpacket ID information, the payload size information and the ARQ
channel ID information. Thereafter, in step 1515, the terminal
determines whether the MAC ID among the acquired control
information is identical to a MAC ID previously assigned from the
base station. If the MAC ID is not identical to the previously
assigned MAC ID, the terminal discards the buffered PDCCH, SPDCCH
and PDCH, judging that the currently received data is not its own
data. If, however, the acquired MAC ID is identical to the MAC ID
assigned from the base station, the terminal demodulates the PDCH
buffered for the subpacket length using the subpacket length
information, subpacket ID information, payload size information and
ARQ channel ID information, acquired in steps 1507 and 1513,
judging that the currently received data is its own data.
FIG. 16 illustrates a structure of a channel transmission device
for transmitting subpacket length information by a base station
according to the third embodiment of the present invention.
Referring to FIG. 16, an encoder 1601 encodes subpacket length
information into coded symbols. For example, a (3,2) block encoder
for block-encoding 2-bit subpacket length information into 3 output
symbols can be used for the encoder 1601. A controller 1602
controls an I/Q channel switch 1603 and Walsh spreaders 1604 and
1605 using Table 3. The switch 1603, under the control of the
controller 1602, switches the symbols from the encoder 1601 to the
I channel (first output line) or the Q channel (second output
line). The Walsh spreaders 1604 and 1605 multiply the symbols from
the switch 1603 by a Walsh function of length 512 from the
controller 1602, for spreading, and outputs 1,536 chips per slot.
As mentioned above, the PPDCCH transmitter spreads the coded
symbols corresponding to the subpacket length information with a
Walsh function based on the MAC ID information, and transmits the
spread coded symbols through a specific transmission channel (I
channel or Q channel). The transmission device is different from
the transmission device of FIG. 11 in that the Walsh function and
the transmission channel are not associated with one MAC ID, but a
plurality of MAC IDs. That is, the second embodiment of the present
invention determines whether the received packet data is its own
packet data by simply demodulating the PPDCCH, whereas the third
embodiment of the present invention determines whether the received
packet data is its own data by demodulating up to the SPDCCH and
analyzing the MAC ID.
FIG. 17 illustrates a structure of a channel transmission device
for transmitting the remaining control information excepting the
subpacket length information by a base station according to the
third embodiment of the present invention. As illustrated, the
"remaining control information" may include MAC ID information,
payload size information, ARQ channel ID information and subpacket
ID information.
Referring to FIG. 17, a convolutional encoder 1701
convolutional-encodes an information bit stream of the remaining
control information into coded symbols. For example, an R=1/2, K=9
convolutional encoder is used for the convolutional encoder 1701.
Therefore, the encoder 1701 receives 12 information bits and
provides 24 output symbols. The controller 1602 controls a sequence
repetition number of a sequence repeater 1702 based on the
subpacket length information. The sequence repeater 1702, under the
control of the controller 1602, sequence-repeats the 24 symbols
from the encoder 1701 a predetermined number of times. A QPSK
modulator 1703 QPSK-modulates the coded symbols from the sequence
repeater 1702 and outputs a complex signal comprised of an
I-channel signal and a Q-channel signal. Walsh spreaders 1704 and
1705 multiply the complex signal from the QPSK modulator 1703 by a
Walsh function of length 128 assigned to the SPDCCH, for Walsh
spreading. Thereafter, the Walsh-spread signal is PN-spread and
converted into a radio frequency. The radio frequency is
transmitted through an antenna.
FIG. 18 illustrates a structure of a channel reception device for
receiving the subpacket length information by a terminal according
to the third embodiment of the present invention. The channel
reception device of FIG. 18 has a structure corresponding to the
channel transmission device of FIG. 16.
Referring to FIG. 18, a controller 1803 reads a Walsh function
corresponding to a MAC ID assigned by the base station from Table 3
and provides the read Walsh function to Walsh despreaders 1801 and
1802. Further, the controller 1803 controls a switching operation
of a switch 1804 by reading transmission channel information from
Table 3. The despreaders 1801 and 1802 despread 1,536 chips
received for one slot with a Walsh function of length 512
determined by the controller 1803, and outputs 3 coded symbols. The
switch 1804 is switched by the controller 1803, thus to provide
outputs of the despreader 1801 or 1802 to an energy detector 1805
and a decoder 1806. The energy detector 1805 measures energy of the
symbols from the switch 1804, and outputs the measured energy value
to the controller 1803. The controller 1803 determines whether the
measured energy value exceeds a predetermined threshold. If the
measured energy value is greater than the threshold, the controller
1803 enables the decoder 1806. However, if the measured energy
value is less than the threshold, the controller 1803 disables the
decoder 1806. The decoder 1806, under the control of the controller
1803, decodes the symbols from the switch 1804 and outputs the
subpacket length information. The subpacket length information is
provided to the controller 1803. For example, a (3,2) block decoder
for block-decoding 3 input symbols and outputting 2 information
bits can be used for the decoder 1806.
FIG. 19 illustrates a structure of a channel reception device for
receiving the remaining control information excepting the subpacket
length information by a terminal according to the third embodiment
of the present invention. The channel reception device of FIG. 19
has a structure corresponding to the channel transmission device of
FIG. 17. The channel reception device of FIG. 19 is enabled when
the measured energy value of the PPDCCH detected by the energy
detector 1805 of FIG. 18 is greater than the threshold.
Referring to FIG. 19, despreaders 1901 and 1902 multiply received
PN-despread signals by a Walsh function of length 128 used for
Walsh spreading of the SPDCCH, for spreading, and output 12 symbols
per slot. A QPSK demodulator 1903 QPSK-demodulates the 12 symbols
from the despreaders 1901 and 1902, and outputs 24 demodulated
symbols per slot. The controller 1803 receives the subpacket length
information from the PPDCCH reception device of FIG. 18, and
determines a sequence repetition number N indicating the number of
slots over which the SPDCCH is transmitted, i.e., how many times
the sequence has been repeated, by consulting Table 4 based on the
subpacket length information. Further, the controller 1803 controls
a sequence combiner 1904 based on the sequence repetition number N.
The sequence combiner 1904, under the control of the controller
1803, generates 24 coded symbols by combining the demodulated
symbols from the QPSK demodulator 1903. A decoder 1905 decodes the
24 coded symbols from the sequence combiner 1904 and outputs the
remaining control information. For example, a R=1/2, K=9
convolutional decoder can be used for the decoder 1905. Here, the
"remaining control information" may include 6-bit MAC ID
information, 2-bit payload size information, 2-bit subpacket ID
information and 2-bit ARQ channel ID information. The controller
1803 compares the MAC ID among the control information with the MAC
ID assigned from the base station. If the MAC IDs are identical to
each other, the controller 1803 demodulates the PDCH. Otherwise, if
they are not identical to each other, the controller 1803 discards
the buffered PDCH data.
As described above, the third embodiment of the present invention
transmits the subpacket length information over the PPDCCH and the
remaining control information over the SPDCCH. Here, the coded
symbols of the PPDCCH are spread with a Walsh function shared by a
plurality of terminals, before transmission.
FIG. 20 is a diagram for explaining an overall operation of a
terminal according to an embodiment of the present invention.
Referring to FIG. 20, a PPDCCH demodulator 2000 measures reception
energy of the PPDCCH and determines whether the measured energy
value exceeds a predetermined threshold. If the measured energy
value exceeds the threshold, the PPDCCH demodulator 2000 acquires
MAC ID information and subpacket length information by demodulating
and decoding the signal received over the PPDCCH. The acquired
subpacket length information is provided to a SPDCCH demodulator
2001 and a PDCH demodulator 2002. Then, the SPDCCH demodulator 2001
acquires the remaining control information by demodulating and
decoding the SPDCCH using the subpacket length information from the
PPDCCH demodulator 2000. In the case of the first and second
embodiments, the acquired remaining control information includes
the subpacket ID information, the ARQ channel ID information and
the payload size information, acquired through demodulation of the
SPDCCH. In the case of the third embodiment, the acquired remaining
control information includes the MAC ID information, the subpacket
ID information, the ARQ channel ID information and the payload size
information, acquired through demodulation of the SPDCCH.
Thereafter, the remaining control information is provided to the
PDCH demodulator 2002. The PDCH demodulator 2002 demodulates the
PDCH using control information acquired through demodulation of the
PPDCCH and the SPDCCH. According to the first embodiment of the
present invention, if the MAC ID acquired by the PPDCCH demodulator
2001 is not identical to the MAC ID previously assigned by the base
station, the SPDCCH demodulator 2001 and the PDCH demodulator 2002
are disabled. In accordance with the third embodiment of the
present invention, if the MAC ID acquired from the SPDCCH is not
identical to the MAC ID assigned from the base station, the PDCH
demodulator 2002 is disabled and the buffered channel data is
discarded.
As described above, the mobile communication system for high-speed
packet transmission according to the present invention can
effectively transmit various control information needed for
demodulation of the packet data channel.
While the invention has been shown and described with reference to
a certain preferred embodiment thereof, it will be understood by
those skilled in the art that various changes in form and details
may be made therein without departing from the spirit and scope of
the invention as defined by the appended claims.
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